Obtaining wide energy-gap semiconductor ultra-thin films is an important aspect for their application in sulfide-based solar cells. By reducing the optical losses associated with light reflection and exhibiting absorption edge shifts towards short wavelengths, these layers can optimize the amount of photons interacting with the active photovoltaic material, which increases the conversion efficiency of the solar cell. Ultra-thin CdS films were prepared by a low-cost chemical synthesis and the impact of silver doping on the optical, structural, and morphological properties was evaluated. SEM micrographs revealed that the layers are ultra-thin, homogeneous and uniform, with a reduction in particle size with increasing doping concentration. X-ray diffraction data confirmed the crystallization of CdS in the hexagonal phase for all prepared samples. A low concentration contributed to the formation of Ag₂S in the monoclinic phase according to the diffractograms. The optical properties of the thin films revealed an absorption edge shift that increased the CdS band gap from 2.267 ± 0.007 to 2.353 ± 0.005 eV with increasing doping concentration, improving the spectral transmittance response. These results make these layers particularly useful for implementation in next-generation flexible photovoltaic devices.

Polycrystalline samples of the dielectric, ferroelectric Na_0.9Li_0.1NbO₃ were synthesized by means of solid-state reaction using different ramps of temperature. High purity precursors Nb₂O₅, Na₂CO₃ and Li₂CO₃ were stoichiometricaly mixed and heated at 1373 K for 6 hours in air atmosphere. The Na_0.9Li_0.1NbO₃ samples were characterized by means of diffraction of X-rays using a Panalytical X'Pert Pro diffractometer. The obtained diffractograms were refined by Rietveld procedure using the software Maud. The results show that Na_0.9Li_0.1NbO₃ crystallizes in an orthorhombic structure (space group Pbma). The refined diffraction patterns also suggest a possible replacement of the Na ions by Li ions in the parent, ferroelectric NaNbO₃ compound. For electrical characterization of the samples, electrical polarization curves were measured using a Radiant Technologies RT66A test system for ferroelectric materials. The polarization versus applied electrical dependence shows a hysteretic behavior verifying the ferroelectric character of the material. A maxima polarization of 130 µC/m² is obtained at room temperature.